Oh drat. When I first read this book, I loved it. I gave it four stars for creativity, characters and plot. I liked the way the authors interwove the facts of the Jack the Ripper case with the events happening to the characters in the book. I loved the steampunk aspects of the entire series. I even understood why the authors found it necessary to invent a whole new character to pin the murders on.
What I do NOT understand is why the authors made a huge historical error (by neglecting one tiny piece of research) for no reason that advances anything in the book. One of the prostitutes who is soon to be murdered goes to Aleister Crowley for help when she feels endangered, and he has sex with her, but can't help her avoid her coming fate. There is nothing in the scene with them which advances the plot or the reader's understanding of any of the characters. It's as if Crowley is dragged into the novel just so the authors can mention his self-awarded reputation as "The Great Beast."
One big problem--Crowley was thirteen years old when the Ripper murders took place. He wasn't in London, wasn't even living on his own. One teensy little websearch by either Asprin or Evans would have turned up this little fact.
You blew it, guys.